Oncologic Safety of Breast-Conserving Surgery Compared to Mastectomy in Patients Receiving Neoadjuvant Chemotherapy for Locally Advanced Breast Cancer

BACKGROUND: Breast-conserving surgery (BCS) in patients with large tumors shrunk by neoadjuvant chemotherapy (NCT) remains controversial. We investigated oncologic outcomes of BCS in patients receiving NCT to treat locally advanced breast cancer (LABC). METHODS: We reviewed 1,994 patients who underwent surgery with/without NCT. Patients were categorized into three groups according to treatment methods: initial BCS, BCS after NCT (NCT-BCS), and mastectomy after NCT (NCT-MX). Their characteristics and outcomes were analyzed. RESULTS: The NCT-BCS group had earlier stage cancer, more hormone receptor-negative and triple-negative breast cancers (TNBC) than the NCT-MX group. However, outcomes did not differ statistically between the two groups. BCS patients receiving NCT were younger, and had more advanced, hormone receptor-negative, HER2-positive, and TNBC breast cancers than BCS patients without NCT. Patients with pathological complete remission (pCR) in the NCT-BCS group had better survival outcomes than non-pCR patients and the initial BCS group. By multivariate analysis in patients receiving NCT, final stage and TNBC were associated with poor overall survival (stage III: P = 0.008; TNBC: P = 0.01), however surgery type was not (P = 0.20). CONCLUSIONS: BCS after NCT is a safe option for LABC that responded well to NCT. Shrinking tumors with NCT allows more opportunities to apply BCS without compromising outcomes.ope